Optical sizing apparatus



Aug. 27, 1940. R. A. COLE 292139924 OPTICAL SIZING APPARATUS Original Filed Jan 9, 1957 2 SheetsSheet 2 a 65 63 4 62 F I J lg 5 K 7 v \I\ 1 4 73 92 10/ 7X 3 f q Z 7 I l 6 2 7 I F 75 116$ 1 o 5 J 6/ a??? 4 o 66 106 I45 6.9 86 1 I 4 70 I luumn '1 f I F l g 8 Z 2" C96 7 5 I56 I67 ll [/0 9? /6 l5 7 \j Zmnentor [4/ RAY/MUN]: AJIULE attorney Patented Aug. 27, 1940 UNITED STATES OPTICAL SIZING APPARATUS Raymond A. Cole, Worcester, Mass., asslgnor to Norton Company, Worcester, Mass, at corporation of Massachusetts Original application January 9, 1937, Serial No.

119,772. Divided and this application January 2'3, 1938, Serial No.

3 Claims.

The invention relates to internal grinding machines, and particularly to automatically actuating size controlling apparatus therefor.

One object of the invention is .to provide a sen- 5 sitive photoelectric sizing apparatus for an internal grinding machine. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the fea-= tures of construction, combinations of elements and arrangements of parts, as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be pointed out in the following claims.

In the accompanying drawings illustrating one of many possible embodiments of the mechanical features of this invention,

Figure l is a front elevation of an internal grinding machine incorporating the invention;

Figure 2 is an electrical diagram;

Figure 3 is a horizontal axial sectional view of the optical apparatus for directing the rays against the work piece;

Figure 1 is a sectional view, taken on the line l---l of Figure 3;

Figure 5 is an optical diagram;

Figure 6 is a perspective view of one of the mirror instrumentalities which includes two re-=' fleeting surfaces; I

Figure 7 is a further optical diagram in which the rays are projected into a single plane for purposes of illustration; and

Figure- 8 is a fragmentary sectional view, on an enlarged scale, showing a portion of the optical apparatus.

Referring first to Figure 1, I provide an internal grinding machine which may be of the general type identified by the trade-mark Size- Matic and which, so far as some of its features are concerned, will be found described in United States Letters Patent No. 1,682,672 and No. 1,682,- 673 but, instead of relying on a predetermined advance beyond the dressing plane to control finished size of work pieces, I substitute the photoelectric apparatus herein particularly to be described. It should be understood, however, that I may embody the sizing apparatus more particularly described herein with any other type of internal grinding machine, for example that disclosed in McDonough Reissue Patent No. 16,141, using one of the gauges thereof to initiate a dressing operation.

Considering now the illustrative embodiment of the present invention, the machine includes a.

(Cl. ill-=14) base is, a work head it mounted on a bridge 12, and a carriage l3 mounted for reciprocatory movement on the base ill under the bridge G2. The machine further includes a wheel head 54 mounted on a cross slide, not shown, which is mounted on the carriage 13 so that the wheel head M may be moved transversely of "the direc== tion of reciprocation oi the carriage 53, that is to say substantially at right angles thereto. The wheel head fi l journals a spindle l5 upon which is mounted a small grinding wheel l6, and any suit able drive for the spindle i5 is provided. The ways supporting the carriage l3 guide the carriage l3 in the direction of the axis of the spindle 05 whereby the grinding wheel is may be advanced into a work piece 28, grind the work piece and thereafter Withdraw to the position shown in Figure 1. The cross feed of the wheel head ill on the carriage 83 is procured by rotation of a screw shaft 2t controlled by a hand wheel 22 and other mechanism more fully described in the patent to Taylor No. 1,682,673 referred to. The rectilinear movement of the carriage l3 may be procured by mechanical actuation or by fluid pressure actuation as, for example, by the use of hydraulic mechanism described in Heald and Guild Patent No. 1,582,468, which includes a cylinder-piston unit, not shown, actuating a piston rod 23 which is connected by a bracket 28 to the carriage 83. Automatic cross feed of the wheel head 54 is, as described in the Taylor patent referred to, achieved by a relative engagement of a cam 25 (adjustably fastened to a bar 26, one end of which is secured to the bridge 12 and the other end of which is secured by means of a bracket 26a to the base it) with a roller, not shown, connected to a pawl 27. Pawl 21 actuates a ratchet wheel connected by reduction gearing to the screw shaft 2|, all as is in detail illustrated in the Taylor patent referred to.

The control of the rectilinear movement of the carriage I3 may be achieved by fluid pressure controlling and reversing mechanism described in aforesaid Patent No. 1,582,468 to Heald and Guild, the reversing valve being controlled by a lever 30 which is interlocked with a reversing lever 31 so that when the lever 30 is to the right, the lever 3| is to the left, as shown in Figure 1, and vice versa. Suitable detents or load-and-flre devices are provided and the lever 38 controls a reversing valve to reverse the direction. of motion of the carriage I3, as will be found described in the aforesaid patent to Heald and Guild, it being now well known to control the motion of a grinding carriage by the actuation of carriage dogs on an interposed reversing lever, such as the lever 3|. The carriage dogs which control the reversing lever 3|, as shown in Figure 1, include a fixed dog 32 adjustably mounted as by means of worm 33 and worm rack 34 on the carriage I3 and a pivotally mounted dog 35 which is capable of lifting over the reversing lever 3| when the carriage is traversed to the left, but will engage the lever 3| when the carriage I3 is traversed to the right and when the lever 3| is between the dogs 32 and 35. The dog 35 is mounted on a sliding block 36 capabe of sliding with respect to the carriage I3 and controlled by a latch 31 which in turn is pivotally connected to a block 38 which is adjustably secured to the carriage I3 by means of a worm 39 and the worm rack 34.

Referring now to Figures 1 and 2, the machine further includes electromagnets 49 and 4|, the former being mounted in front of the latter, and both being mounted on the front of the machine, as shown in Figure 1. These electromagnets control levers t2 and 93. The lever 42 is in the vertical plane of the latch 31. The lever 63 is in the vertical plane of the dog 35. When the lever 92 is lifted, the latch 31 will be raised, thus to allow the block 36 to slide, relatively, along the carriage I3, extending the reciprocatory traverse stroke of the grinding wheel I6 to pass it by a dressing diamond 45 which is at that time lowered into the path of travel of the wheel I6. Raising of the lever 83 causes the dog 35 to pass over the reversing lever 3| to extend the stroke of the carriage I3 to the right, thereby to cause the grinding action to cease, the carriage I 3 being stopped in the withdrawn position by devices not shown herein. The dressing diamond 65 is mounted on an adjustable screw plug 96 which in turn is carried by a swinging member 91 mounted on a trunnion 48 provided by a. suitable standard 69 rising from the stationary frame of the machine. When the lever arm 92 is moved, a downward extension 59 thereof moves a valve 5|, thus making the pressure fiuid active against the piston, not shown, which is connected by means of a link 52 to the member 91, so that when the electromagnet 60 is operated, the stroke of the grinding wheel I6 is extended and as it starts outwardly, the diamond 65 moves into its path, thereby to procure a dressing operation.

The foregoing instrumentalities are now well known in grinding machines, are described in the patents referred to and in others and embodied in many machines now on the market, and

therefore I do not described the same in more detail. In the present embodiment of this invention, the grinding wheel I6 is advanced into the work piece 20 and grinds with a reciprocatory stroke just long enough to effect the grinding action and, after preliminary grinding has been achieved, the automatic dressing indicated is effected, whereupon the wheel I6 returns into the work piece for the final and finishing cuts. The wheel I6 is finally removed from the work piece by energization of magnet 9| which lifts the dog 35, and magnet 4| is controlled by the size controlling apparatus now particularly to be described. During the outward movement of the carriage I3 at the end of a grinding operation, compensation of the cross slide is achieved in a manner fully described in Taylor Patent No. 1,682,673 whereby the vertical plane of the cutting line of the grinding wheel on the work piece at finished size will bear substantially the same relation to the vertical plane of the dressing line throughout the grinding of a whole series of work pieces ground to the same size. Accordingly, the

specific compensation mechanism of the Taylor patent need not be in detail described herein.

Referring now to Figure 1, the work piece 26 is held by means of a suitable chuck 60 which is mounted on the end of a work spindle 6|. Referring now to Figure 3, the spindle 6| is journailed in journals 62 and 63 incorporated in the work head II. Fastened to the spindle 6| is a pulley 64 by means of which the spindle 6| may be rotated by a belt drive, not shown. Extending rearwardly from the journal member 63 in the work head II are brackets 65 and 66. These brackets 65 and66 have slideways 61 and 69, respectively, supporting a slide 69 which is shaped in the form of the capital letter D, as shown in Figure 4. Extending between the top and bottom of the slide 69, as shown in Figures 3 and 4, is a rock shaft 10 upon which is mounted an optical tube 1|. Extending rearwardly from the optical tube 1| is an arm 12 through which extends a rod 13 having a spring 19 thereon which engages the arm. The spring 19, which is backed up by a nut 15, urges the arm and also the optical tube 1| in a clockwise direction, Figure 3. The front end of the rod 13 is supported by a resilient bar 89 having a notch 8| in a position to engage a detent 82 on the arm 12. The arm 12 may be used as a handle to swing the optical tube 1| in a counterclockwise direction and the detent 82 and the notch 8| will hold it there. This facilitates the introduction into and removal of work pieces from the chuck 60.

Still referring to Figure 3, the tube 1| has a central partition 85. On one side of this partition 85 is a camera chamber 86 for the passage of light. On the other side of the partition is a tube 81 forming another camera chamber for the passage of light. The tube 81 is supported by a plurality of partitions 88 which, as shown in Figure 4, surround the tube 81 and extend between it and the inside of the tube 1|. At the ends of the tube 1| are right angle extensions 89 and 90, respectively. In the right angle chamber 89 and firmly fastened in place is a lamp 9| having a point source of illumination 92. The lamp 9| is an incandescent electric lamp, the filaments 93 of which are dark, all light being given from the point 92. The point 92 is located in the axis of the tube 81. In the tube 81 are suitably fastened a pair of condensing lenses 96 and 91. These are lenses which have substantially spherical surfaces to refract the light in two dimensions to direct the rays toward a true focus. In front of them and mounted in the tube 81 is a color filter I00 to eliminate all rays excepting those of one color, in order that diffusion of light by refraction of the different wave lengths at different angles will be avoided to a suflicient extent. In the tube 61 is also a condensing lens II which may be of the same general type as lenses 96 and 91, but in the present illustrative embodiment of the invention it is shown as a double convex lens whereas the lenses 96 and 91 are single convex lenses. Referring now to Figure 5, three rays of light will be traced, these being designated a, b and c. The ray a is the central ray and'the rays b and c are marginal rays. The ray a passes through all three lenses 96, 91 and IDI and also the color filter I00 without being deviated from its straight line course. It next passes through a double concave lens I02, also suitably fastened in the tube 81, without being diverted from its straight line course. The rays b and 0, however, were altered from their path of divergence by the lenses 96 and 91, being brought into parallelism with the ray a between the lenses 9'! and IOI. The lens I 0| brought the rays 17 and c toward a focus. Considering the light now as a beam, it started out as a diverging beam from the source of light 92, as every luminous body sends rays in all directions. The lamp 9| should have its glass painted black excepting in the very small circle sufficient to send forth enough light to cover the face of the lens 56. The lenses 96 and 91 produced a beam with parallel rays. The lens IOI brought this beam towards a focus. Before it came to a focus, this beam passed through the double concave lens I02 which changed it into a beam of parallel rays again. The reason for condensing the beam that existed between the lenses 91 and MI, thereafter to cause it to reassume the form of a beam with parallel rays, is in order to intensify the light, or stating this in another way, in order to collect as many rays as possible to form a strong beam of light. The beam in the tube 81 is a beam all the rays of which are substantially in parallelism. It will be recognized that this is a condition the complete attainment of which is not possible but by providing a point source of light, triple condensing lenses and a double concave lens, this desired condition is achieved for the practical purposes of this invention. The beam after the lens 502 may also be described as a beam the focus of which is at infinite distance from the lens l02.

Referring now to Figures 3, 5 and 8, at the front or right-hand end of the tube 8l' is a double convex lens I05 of characteristics quite different from the lenses 96, 91 and NI. This lens I05 is a cylindrical lens; that is to say, its outline is that of a parallelogram when seen from above, as in Figures 3 and 5. However, when seen from in front, it looks like the lens I M. This lens i05 causes the rays to converge in a vertical plane but not in a horizontal plane. In my apparatus the lens M5 is complementary to the cylindrical Work piece surface in that the efiect of the two when the work piece is at the desired size, is to produce a final parallel ray beam.

Considering further Figures 3 and 4, to the inside of the tube ll I fasten a mirror fixture 906 comprising a base portion I07 which may be screwed to the tube H and a glass wedge 508 secured thereto which has integrally connected thereto a non-rectangular parallelepiped i09 of glass. The wedge I08 and the parallelopiped i09 have reflecting surfaces IIO and HI which form dihedral angles with the fiat surface N2 of the base ill? of 135. Surfaces H0 and HI may be silvered surfaces. Light from the lens I05 is directed onto the surface III and thereby is turned at right angles into the plane of revolution of the work piece. This light is reflected and some of it is reflected by the surfaces H0 into a pair of beams, all the rays of which are parallel, passing through the camera chamber 86. In the camera chamber 86 and at 135 to the axis thereof is a mirror H5 in line with holes II6 in the wall 05, tube 81 and tube II. From the mirror I I5, the light passes to various other mirrors and finally to a photoelectric cell I20. But beams with parallel rays, 1. e. with focal length at infinity, leave the mirror IIO only when the work piece 20 is at predetermined finished size, as will now be explained in connection with Figure 7, which is an illustration of the light rays in projection. Since the projection plane of Figure 7 is not identical with the diagrammatic view of Figure 5, the rays a, b and 0 cannot be identitled. However, rays a, y, 2, x, y and z are identified in Figure 7, and these rays represent rays actually approaching the work piece 20 toward the finished surface 20' thereof between said surface and the mirror III; beyond the mirror III they are shown in their in age positions, that is to say with their incident paths projected backwards. Construction circles ma, ya and 2a are drawn inFigure 7 tangent to rays :2, y, z, :r, y and 2'. It will be seen that upon reflection from the surface 20', rays 2, y, z, m, 11' and z are tangent to the other sides of the circles so, ya and za. The reflected paths of these rays are parallel to each other. However, with the work piece surface at 20", the rays at, y, 2, at, y and 2, upon reflection, assume the positions indicated by the dotted lines. These rays are not in parallelism and the reflected beam comes to a focus f. The beam has a focal length which has a small finite value, in inches. After passing the focal point I, the rays are absorbed in the walls of the various tubes through which they pass. In order to produce a reflected beam whose rays are in parallelism from a beam the rays of which are in parallelism, lens I05 and the mirror iii are placed in the relative positions shown to produce converging rays :0, y, z, z, y and 2' having focal point f in the mirror HI relative to the circle of the work piece, as shown in Figure 7, and it is sufficient that the lens l05 be of a convexity and index of refraction to bring the rays to this focal point. As the focal point I has a definite geometrical relation, shown in Figure 7, to the circle 20' of the finished work piece, this relation is destroyed for any other size of work piece, such as is represented by the circle 20", and therefore only when the work piece is at a given finished size will the rays be reflected from the surface thereof as a parallel beam with focal length infinity. The mirror HI intercepts a part of this parallel beam but the two side portions thereof are picked up by the mirrors H0, H0 and sent along the tube ii in the camera chamber 86. As is shown in Figure 7, a large cross-sectional area of the original beam is directed toward the mirrors H0, H0.

The walls of the camera chamber 86 as well as the interior wall of the tube 81 are painted with a dull black paint, such as any paint having a carbon pigment without a glossy surface, so that all rays which strike these walls will be, as much as possible, absorbed. After leaving the mirror M5, the rays of the beam of light or parallel beams of light are reflected by a mirror I25 whose position is indicated in Figure l and which is placed at an angle of to the horizontal so that the light will be reflected downwardly in a vertical direction. The mirror I25 is at the top of a tube I26 which is held by the machine base I0, as shown in Figure 1. The interior wall of the tube I26 is likewise painted with a dull black pigment paint. At the bottom of the tube I26 is a mirror I2! at the junction of this tube I26 with a tube I28. Tube I28 extends along the entire length of the machine base and at the right-hand end thereof is a mi ror I29 which is also at the bottom of a tube I30. At the top of the tube III is a mirror I 3i which is also at the right-hand end of a. tube I32. At the left-hand end of the tube I32 is located the casing I 33 that holds the photoelectric cell I20. The mirrors I29 and lil are at 45 angles, as shown in Figure 1, so that light is directed from the tube I20 into the tube I30 and then axially into the tube I32. Tubes I28, I30 and I32 are likewise painted black inside.

the tubes at any time, and consequently only at' the moment when the focallength of the light beam is substantially infinity will any light at all reach the photoelectric cell I20.

Referring now to Figure 4 and 8, the extension 90 is formed by horizontal upper and lower walls- I40 which are of a hard material such as hardened steel and bear against the inside of the work piece 20. Extension 90 also has side walls I4I which are preferably of rubber. The steel walls I40 bear against the work piece and determine the position of the tube H which is urged in a clockwise direction, Figure 3 by the spring 14. These walls I40 together with the walls I keep cooling water out of the extension 90, at least to a very considerable extent. The walls I4I, however, will readily deform slightly to conform to the different curvatures of the work piece during grinding. It will be appreciated that the relative change in size of the work piece, as indicated in Figure '1, is grossly exaggerated, to the end that the principles of the invention may be made readily apparent. In order to prevent the tube H from vibrating as the work piece 20 is revolved, I provide a support I which, as shown in Figure 1, may be hinged at I46 to a bracket I41 that is bolted to the work head If. This support I45 is in the form of a bent arm which may be swung into and out of position, being held in operative position by means of spring clamps I49. This support I45 rests under a. cylindrical boss I50 integral with a screw cover I5I which closes the right-hand end of the tube II.

The lenses 96, 91, I! and I02 may be cemented in place in the tube 81 because once the light beam in the tube 81 has been brought to a condition of focal length infinity, there is no further occasion for adjustment. However, in order that this condition may be achieved in each new piece of apparatus despite unavoidable variations in manufacturing operations, the lamp 9I is preferably made adjustablein a direction parallel with the axis of the tube 81. This adjustment may be achieved in any suitable manner, not herein indicated, as by the use of holding screws extending into slots.

It is, however, desirable that the apparatus be adjustable so that it may be used to grind work pieces to different internal diameters. Accordingly the lens I 05 is adjustable in the tube 81 by means of the construction shown in Figure 8. The lens I05 is cemented to a metal annulus I through which pass a pair of adjusting screws I56 with knurled heads, these screws I56 extending also into threaded bores in integral lugs I51 located in the inside of the tube 81. Screws I56 are rotatable in the annulus I55 butare axially immovable relative thereto, as by the provision of collars I60 press fitted onto the screws I56. The annulus I 55 is secured to the inside of the telescoping tube I6I. By turning the screws I56 substantially together, the tube I 6| may bev moved axially in the tube 81. However, the relative angular position of the tubes 81 and I6I is unchanged and, therefore, the relative angular position of the lens I05 is not disturbed by the adjustment. The adjustment moves the center of the lens I towards and away from the surface III and, therefore, adjusts the focal line of the crossing beam relative to the surface of the work piece towards which the beam is directed.

Considering now one electric circuit which may respond to light impinging upon the cathode I64 of the photoelectric cell I20, and referring to Figure 2, a 110 volt A. C. line I65 has connected to it conductors I66 and I61 leading to terminals I68 and I69 of a transformer primary I10. Three secondary coils I1I, I12 and I 13 are energized by the primary coil I10. A non-inductive potentiometer resistance I14 is connected across conductors I15 and I16 of the coil I1I. Conductor I15 leads to the anode I11 of the photoelectric cell I20. Conductor I16 leads to a condenser I18 which is connected by conductor I19 to conductor I which connects to cathode I64 of the photoelectric cell I20.

Secondary coil I12 energizes filament I83 of an amplifying or triode tube I84. A grid I85 of the tube I84 is connected by a conductor I 66 to a non-inductive resistor I81, the other end of which is connected to the conductor I80. A plate I in the tube I84 is connected to a conductor I9I which is connected to a terminal I92. The secondary I13 has one end thereof connected to a terminal I93. Connected in parallel by the terminals I92 and I93 are a condenser I94 and a sensitive relay coil I95. The other end of the secondary coil I13 is connected to a conductor I96 which connects to the movable element I91 of potentiometer I14. Conductor I96 is also connected by a lead I98 to the mid point of coil I12. It will now be seen that a certain degree of illumination of the photoelectric cell cathode I64 causes energization of relay coil I and the apparatus is adjustable by means of the potentiometer I14-I91.

In so much as the energization of the relay I95 may be momentary, I have further provided a relay to close and keep closed the final circuits upon any energization whatsoever of the sensitive relays. As shown in Figure 2, the conductor I66 also connects to a terminal 200. Conductor I61 connects to a relay coil 20I. The other end of the relay coil 20I is connected to a terminal 202. A pendulum contactor 203 is adapted to connect terminals 200 and 202 and this contactor is arranged to be operated by a long arm 204 of an armature 205 actuated by the coil I95. Therefore, energization of the relay coil I95, even momentarily, closes a knife switch 201 electromagnetically operated by the coil 20I. Knife switch 201 connects a conductor 206 to ground. The conductor 208 is connected to one terminal of the electromagnet 4|, the other terminal of which is connected by a conductor 209 to one bar 2I0.of a switch 2 which will be found described in the Taylor patent referred to and which is provided for the purpose of preventing continuous dressing of the grinding wheel. When the grinding wheel has taken the final and finishing strokes on the work piece, a contact plate 2! 2 of the movable element 2 I3 of the switch 2 connects a bar 2I4 with the bar 2I0, thus to connect the conductor 209 to a conductor 2I5 connecting to a generator 2I6, the other terminal of which is ground, as shown in Figure 2. This generator 2I6 is a direct current generator but in certain cases the alternating current lines I65 may be substituted for the generator M 6.

Briefly recapitulating the action of the machine, the operator, after having placed an unground work piece 20 in the chuck 60, moves the lever 12 to swing the right-hand end of the tube H toward the work piece until the upper and lower walls I40 of the extension contact the work piece. Having secured the cover Iii in place, the operator swings the support 5 into the position shown in Figure 3 where the tube II and all other parts are duly supported against vibration. The operator then causes the work piece 20 'to be revolved in the usual manner and, moving the main control lever 20 to the left, causes the grinding wheel IE to enter the work piece to start the grinding operation. Thereafter, automatically, as described in the Taylor patent referred to, a dressing operation takes place whenever a cam 220 operated by the cross feed engages a lever 22! connecting a conductor 222 which is grounded to a conductor 223 which is connected by way of conductor 224 to the electromagnet 40. As the. carriage 13 moves to carry.

the wheel l6 to be dressed by the diamond 45, an arm 225 carried by the block 38 engages the movable element 2l3 of the switch 2 and deenergizes the magnet 40 which prevents further dressing until a new work piece is placed in the machine. Thereafter the flnal and finishing cuts are taken until such time as the rays of light from the point source 52 are, upon reflection from the work piece, of such great focal length that they ultimately reach the cathode I64 of the photoelectric cell I20 whereupon, as already described, circuits are closed which cause energization of the magnet 4| which trips the reversing dog 35, causing the carriage l3 to move to the right to the position shown in Figure 1, removing the grinding wheel 16 from the work piece.

By the provision of the various tubes described, the light is caused to travel along distance to the photoelectric cell I20 which makes the apparatus extremely sensitive. The gauging device is spring-pressed against a surface of the work piece and, furthermore, is located in fixed position in a vertical plane by the supporting member I45. The entire apparatus can be adjusted by moving the D shaped slide 69 in the ways 65, 66, as by means of aifiusting screw 230.

This is a division of my copending application Serial No. 119,772 flied January 9, 1937, now Patent No. 2,121,729.

It will thus be seen that there has been provided by this invention apparatus and a method in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In apparatus for determining the size of the cylindrical bore of an article which cylindrical bore has a reflecting surface, a source of light, means to condense the rays thereof to form a substantially parallel ray beam, means to converge the parallel ray beam in a single plane of its axis only, a first mirror positioned in the beam to direct the rays thereof on to the cylindrical,

bore, a second mirror arranged to receive the beam after reflection from the surface of the bore, the position of said converging means in the beam being such that the convergence of the rays is in a plane at right angles to the axis of the bore, the convergence being such that the work piece reflects substantially parallel rays when and only when the cylindrical bore is of a predetermined size, and means including a photoelectric cell positioned to receive the beam after reflection from the second mirror and said cell being optically spaced from the second mirror a distance such that the cell receives only substantially parallel rays.

2. In apparatus for determining the size of the cylindrical bore of an article which cylindrical bore has a reflecting surface,.a source of light, means to condense the rays thereof to form a substantially parallel ray beam, means to converge the parallel ray beam in a single plane of its axis only, a mirror positioned in the beam to direct the rays thereof on to the cylindrical bore, the position of said converging means in th beam being such that the convergence of the rays is in a plane at right angles to the axis of the bore, the convergence being such that the work piece reflects substantially parallel rays when and only when the cylindrical bore is of a predetermined size, and means including a photoelectric cell positioned to receive the beam after reflection from the work piece and said cell being optically spaced from the work piece a distance such that the cell receives only substantially parallel rays.

3. In apparatus as claimed in claim 2 the combination with the parts and features therein specified of a housing containing the elements other than the cell specified in said claim and a member on said housing contacting the bore of the work piece whereby accurately to position the elements with respect to said bore.

RAYMOND A. COLE.

. CERTIFICATE OF CORRECTION Patent No. 2,215,"o2h. I August 27, 19m.

' r RAYMOND A. 'COLE.

It is hereby certified that error appears in the printed specification of the abovenumbered patent requiring correction as follows: Page 5, first column, line 52, strike out the words "and a method"; and that the said Letters Patent should be' read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 214th day of- June, A. 'D." 191m.

Henry Van Arsdale, (Seal) Acting Connnissioner of Patents.

- CERTIFICATE OF CORRECTION.

Patent No. 2,215,02h. Auguet 2?, 191m.

RAYMOND AQ-coLE'."

It is hereby certified" that error 'appeere in the printed specifio ation of the above numbered patent requiring correction as follower Page 5, first I column, lihe 2, strike out the words "and a method"; and that the said Letters Patent should be' read with this correction therein that the same may conform to the record of the case in the Patent Office. 7 1

Signed and sealed this 21 .th dey of- June, A. 13.1 19!;1.

Heriry Van Arsdale, (Seal) Acting Commissioner of Patents. 

